1. Field of the Invention
The present invention relates to novel lightly cross-linked, network polymeric systems and method of forming and using same to absorb oils.
2. Description of the Prior Art
There has recently been great concern with improving oil absorbing materials, especially the oil spill off the coast of Santa Barbara, Calif. and other areas where oil has presented a problem with regard to water pollution. One clean-up approach has involved the utilization of polyurethane foams to absorb the oil from the surface of water. Another method involves absorbing oil with a mixture of oleophilic shredded rubber tires and particulate polystyrene scraps as disclosed in U.S. Pat. No. 3,567,660. The resulting absorbate is then converted to an asphalt-like material. Apparently, the liquid oil coalesces around the sorbent rubber particles to form large coherent agglomerates. Another approach, disclosed in U.S. Pat. No. 3,314,903, relates to absorbing oil by forming an in situ oil extended polyurethane foam. The oil is mixed together with a liquid polyol, an aromatic diisocyanate, an emulsifier, a catalyst and a blowing agent. The resulting mixture foams and incorporates the oil into the polyurethane foam.
In all of the prior art methods heretofore disclosed, the oil absorbing products such as the foamed material or the shredded tires and polystyrene, for example, have limited oil absorption capabilities. In other words, the utilization of polymers for adsorption or absorption was particularly dependent upon the available material and the polymers were not specially formulated for this purpose. Prior polyurethane foams have structural integrity and strength and therefore there must be sufficient cross-linking of the polyol material to form a fairly rigid solid. Thus, prior art foams were highly cross-linked in the belief that such was required. However, it has been found here for many oil absorbing situations, the polymer need not have any significant strength and thus a minimum of cross-linking would be sufficient. The polymer, even when it has little structural strength can still provide: (1) a high surface to thickness ratio so as to maximize the absorption surface available, and (2) an enhancement of absorption capacity achieved by the further presence of the holes in the foam. In view of the above discussion, it can be seen that though polymer systems were used to absorb oil, none of the prior art techniques provided for an extremely high absorbency of oil per unit of polymeric material utilized.